1. Field of the Invention
The present invention pertains to the field of computer systems. More specifically, the present invention relates to cooling apparatuses for cooling components that generate heat in computer systems.
2. Description of Related Art
Portable computer systems are generally designed compact for ease of transportation. Portable computer systems also typically operate using a set of transportable batteries that supply energy for operation of various components in the portable computer systems.
Portable computer systems include components such as processors that generate heat when the portable computer system is in operation. Earlier processors developed until 1980s typically generated heat in the 2-3 Watts range. Today, modern processors can generate heat exceeding 10 Watts. Modern processors are generating such excessive heat because of the inclusion of a large number of transistors and the high speed at which they operate.
The excessive heat generated by modern processors can raise the operating temperature of the processors above a manufacturer recommended threshold temperature if the heat is not properly dissipated. Heated processors can malfunction and generate incorrect results. The reliability of heated processors can also be degraded. It is important, therefore, to dissipate the heat generated by the processors in order to maintain the operating temperature of the processors below the recommended threshold temperature.
Cooling systems have been employed in prior computer systems to dissipate the heat generated by the processors. The cooling systems are generally designed to dissipate a sufficient amount of heat to maintain the operating temperature of processors below the recommended threshold temperature.
One prior cooling system includes a heat sink comprising a heat transfer surface. The heat sink is typically positioned on a printed circuit board which also houses other components, such as memory and processor. A base casing generally encloses the printed circuit board and the components mounted on the printed circuit board. The heat sink is thermally coupled to the processor and thus provides additional heat transfer surface area for dissipating heat generated by the processor.
However, the amount of heat transfer surface area that can be provided by the heat sink is limited because there is only a fixed amount of space on the printed circuit board and several components share that fixed space. Such limited heat transfer surface area is not typically sufficient to dissipate adequate amount of heat to maintain the operating temperature of the processor below the recommended threshold temperature. Also, the limited air circulation in the base casing limits the heat dissipation.
Some prior cooling systems have further employed a fan to increase the air circulation around the heat sink. The increased air circulation typically causes increased heat dissipation from the heat sink. The fan is also generally mounted on the printed circuit board in the base casing.
Unfortunately, cooling systems which utilize fan and heat sink are undesirable in portable computer systems because of space and power requirements. The base casing may need to be designed with more height to accommodate the fan. Such increased height of the base casing makes portable computer systems less convenient for transportation. Further, the heat sink and the fan together occupy excessive space on the printed circuit board. The limited space availability on the printed circuit board may force the designer of the computer system not to include other components on the printed circuit board.
Moreover, the fan consumes considerable energy. The additional energy is generally supplied from the batteries which also supply energy for other components of the portable computer system. Since the batteries store only a limited amount of energy, such additional energy consumption for the fan decreases the lifetime of the batteries. In addition, fans typically have a higher failure rate than other components of the computer system, making the overall computer system less reliable.
Another prior cooling system increases heat dissipation by using a base casing made of thermally conductive material such as magnesium. A thermally conductive path is provided between the processor and the base casing. The base casing generally has several surfaces that are exposed to the air outside of the computer system. The conductive surfaces of the base casing dissipate the heat generated by the processor.
Unfortunately, conductive material such as magnesium is generally expensive which results in an increased cost of the overall portable computer system. In addition, the base casing does not have sufficient surface area to dissipate high amounts of heat generated by modern processors.